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ntpdc(8) System Manager's Manual ntpdc(8)
NAME
ntpdc - special NTP query program
SYNOPSIS
ntpdc [ -46dilnps ] [ -c command ] [ host ] [ ... ]
DESCRIPTION
ntpdc is used to query the ntpd daemon about its current state and to
request changes in that state. The program may be run either in inter-
active mode or controlled using command line arguments. Extensive state
and statistics information is available through the ntpdc interface. In
addition, nearly all the configuration options which can be specified
at startup using ntpd's configuration file may also be specified at run
time using ntpdc.
If one or more request options are included on the command line when
ntpdc is executed, each of the requests will be sent to the NTP servers
running on each of the hosts given as command line arguments, or on
localhost by default. If no request options are given, ntpdc will
attempt to read commands from the standard input and execute these on
the NTP server running on the first host given on the command line,
again defaulting to localhost when no other host is specified. ntpdc
will prompt for commands if the standard input is a terminal device.
ntpdc uses NTP mode 7 packets to communicate with the NTP server, and
hence can be used to query any compatible server on the network which
permits it. Note that since NTP is a UDP protocol this communication
will be somewhat unreliable, especially over large distances in terms
of network topology. ntpdc makes no attempt to retransmit requests, and
will time requests out if the remote host is not heard from within a
suitable timeout time.
The operation of ntpdc are specific to the particular implementation of
the ntpd daemon and can be expected to work only with this and maybe
some previous versions of the daemon. Requests from a remote ntpdc pro-
gram which affect the state of the local server must be authenticated,
which requires both the remote program and local server share a common
key and key identifier.
Note that in contexts where a host name is expected, a -4 qualifier
preceding the host name forces DNS resolution to the IPv4 namespace,
while a -6 qualifier forces DNS resolution to the IPv6 namespace.
COMMAND LINE OPTIONS
Specifying a command line option other than -i or -n will cause the
specified query (queries) to be sent to the indicated host(s) immedi-
ately. Otherwise, ntpdc will attempt to read interactive format com-
mands from the standard input.
-4 Force DNS resolution of following host names on the command
line to the IPv4 namespace.
-6 Force DNS resolution of following host names on the command
line to the IPv6 namespace.
-c command
The following argument is interpreted as an interactive format
command and is added to the list of commands to be executed on
the specified host(s). Multiple -c options may be given.
-d Turn on debugging mode.
-i Force ntpdc to operate in interactive mode. Prompts will be
written to the standard output and commands read from the stan-
dard input.
-l Obtain a list of peers which are known to the server(s). This
switch is equivalent to -c listpeers.
-n Output all host addresses in dotted-quad numeric format rather
than converting to the canonical host names.
-p Print a list of the peers known to the server as well as a sum-
mary of their state. This is equivalent to -c peers.
-s Print a list of the peers known to the server as well as a sum-
mary of their state, but in a slightly different format than
the -p switch. This is equivalent to -c dmpeers.
INTERACTIVE COMMANDS
Interactive format commands consist of a keyword followed by zero to
four arguments. Only enough characters of the full keyword to uniquely
identify the command need be typed. The output of a command is normally
sent to the standard output, but optionally the output of individual
commands may be sent to a file by appending a <, followed by a file
name, to the command line.
A number of interactive format commands are executed entirely within
the ntpdc program itself and do not result in NTP mode 7 requests being
sent to a server. These are described following.
? [ command_keyword ]
help [ command_keyword ]
A ? by itself will print a list of all the command keywords
known to this incarnation of ntpq. A ? followed by a command
keyword will print function and usage information about the
command. This command is probably a better source of informa-
tion about ntpq than this manual page.
delay milliseconds
Specify a time interval to be added to timestamps included in
requests which require authentication. This is used to enable
(unreliable) server reconfiguration over long delay network
paths or between machines whose clocks are unsynchronized.
Actually the server does not now require timestamps in authen-
ticated requests, so this command may be obsolete.
host hostname
Set the host to which future queries will be sent. Hostname may
be either a host name or a numeric address.
hostnames [ yes | no ]
If yes is specified, host names are printed in information dis-
plays. If no is specified, numeric addresses are printed
instead. The default is yes, unless modified using the command
line -n switch.
keyid keyid
This command allows the specification of a key number to be
used to authenticate configuration requests from ntpdc to the
host(s). This must correspond to a key number which the
host/server has been configured to use for this purpose (server
options: trustedkey, and requestkey). If authentication is not
enabled on the host(s) for ntpdc commands, the command "keyid
0" should be given; otherwise the keyid of the next subsequent
addpeer/addserver/broadcast command will be used.
quit Exit ntpdc.
passwd This command prompts you to type in a password (which will not
be echoed) which will be used to authenticate configuration
requests. The password must correspond to the key configured
for use by the NTP server for this purpose if such requests are
to be successful.
timeout milliseconds
Specify a timeout period for responses to server queries. The
default is about 8000 milliseconds. Note that since ntpdc
retries each query once after a timeout, the total waiting time
for a timeout will be twice the timeout value set.
CONTROL MESSAGE COMMANDS
Query commands result in NTP mode 7 packets containing requests for
information being sent to the server. These are read-only commands in
that they make no modification of the server configuration state.
listpeers
Obtains and prints a brief list of the peers for which the
server is maintaining state. These should include all config-
ured peer associations as well as those peers whose stratum is
such that they are considered by the server to be possible
future synchronization candidates.
peers Obtains a list of peers for which the server is maintaining
state, along with a summary of that state. Summary information
includes the address of the remote peer, the local interface
address (0.0.0.0 if a local address has yet to be determined),
the stratum of the remote peer (a stratum of 16 indicates the
remote peer is unsynchronized), the polling interval, in sec-
onds, the reachability register, in octal, and the current
estimated delay, offset and dispersion of the peer, all in sec-
onds. The character in the left margin indicates the mode this
peer entry is operating in. A + denotes symmetric active, a -
indicates symmetric passive, a = means the remote server is
being polled in client mode, a ^ indicates that the server is
broadcasting to this address, a ~ denotes that the remote peer
is sending broadcasts and a * marks the peer the server is cur-
rently synchronizing to.
The contents of the host field may be one of four forms. It may
be a host name, an IP address, a reference clock implementation
name with its parameter or REFCLK(implementation number, param-
eter). On hostnames no only IP-addresses will be displayed.
dmpeers A slightly different peer summary list. Identical to the output
of the peers command, except for the character in the leftmost
column. Characters only appear beside peers which were included
in the final stage of the clock selection algorithm. A . indi-
cates that this peer was cast off in the falseticker detection,
while a + indicates that the peer made it through. A * denotes
the peer the server is currently synchronizing with.
showpeer peer_address [...]
Shows a detailed display of the current peer variables for one
or more peers. Most of these values are described in the NTP
Version 2 specification.
pstats peer_address [...]
Show per-peer statistic counters associated with the specified
peer(s).
clockinfo clock_peer_address [...]
Obtain and print information concerning a peer clock. The val-
ues obtained provide information on the setting of fudge fac-
tors and other clock performance information.
kerninfo
Obtain and print kernel phase-lock loop operating parameters.
This information is available only if the kernel has been spe-
cially modified for a precision timekeeping function.
loopinfo [ oneline | multiline ]
Print the values of selected loop filter variables. The loop
filter is the part of NTP which deals with adjusting the local
system clock. The offset is the last offset given to the loop
filter by the packet processing code. The frequency is the fre-
quency error of the local clock in parts-per-million (ppm). The
time_const controls the stiffness of the phase-lock loop and
thus the speed at which it can adapt to oscillator drift. The
watchdog timer value is the number of seconds which have
elapsed since the last sample offset was given to the loop fil-
ter. The oneline and multiline options specify the format in
which this information is to be printed, with multiline as the
default.
sysinfo Print a variety of system state variables, i.e., state related
to the local server. All except the last four lines are
described in the NTP Version 3 specification, RFC-1305. The
system flags show various system flags, some of which can be
set and cleared by the enable and disable configuration com-
mands, respectively. These are the auth, bclient, monitor, pll,
pps and stats flags. See the ntpd documentation for the meaning
of these flags. There are two additional flags which are read
only, the kernel_pll and kernel_pps. These flags indicate the
synchronization status when the precision time kernel modifica-
tions are in use. The kernel_pll indicates that the local clock
is being disciplined by the kernel, while the kernel_pps indi-
cates the kernel discipline is provided by the PPS signal.
The stability is the residual frequency error remaining after
the system frequency correction is applied and is intended for
maintenance and debugging. In most architectures, this value
will initially decrease from as high as 500 ppm to a nominal
value in the range .01 to 0.1 ppm. If it remains high for some
time after starting the daemon, something may be wrong with the
local clock, or the value of the kernel variable tick may be
incorrect.
The broadcastdelay shows the default broadcast delay, as set by
the broadcastdelay configuration command.
The authdelay shows the default authentication delay, as set by
the authdelay configuration command.
sysstats
Print statistics counters maintained in the protocol module.
memstats
Print statistics counters related to memory allocation code.
iostats Print statistics counters maintained in the input-output mod-
ule.
timerstats
Print statistics counters maintained in the timer/event queue
support code.
reslist Obtain and print the server's restriction list. This list is
(usually) printed in sorted order and may help to understand
how the restrictions are applied.
ifstats List interface statistics for interfaces used by ntpd for net-
work communication.
ifreload
Force rescan of current system interfaces. Outputs interface
statistics for interfaces that could possibly change. Marks
unchanged interfaces with ., added interfaces with + and
deleted interfaces with -.
monlist [ version ]
Obtain and print traffic counts collected and maintained by the
monitor facility. The version number should not normally need
to be specified.
clkbug clock_peer_address [...]
Obtain debugging information for a reference clock driver. This
information is provided only by some clock drivers and is
mostly undecodable without a copy of the driver source in hand.
RUNTIME CONFIGURATION REQUESTS
All requests which cause state changes in the server are authenticated
by the server using a configured NTP key (the facility can also be dis-
abled by the server by not configuring a key). The key number and the
corresponding key must also be made known to ntpdc. This can be done
using the keyid and passwd commands, the latter of which will prompt at
the terminal for a password to use as the encryption key. You will also
be prompted automatically for both the key number and password the
first time a command which would result in an authenticated request to
the server is given. Authentication not only provides verification that
the requester has permission to make such changes, but also gives an
extra degree of protection again transmission errors.
Authenticated requests always include a timestamp in the packet data,
which is included in the computation of the authentication code. This
timestamp is compared by the server to its receive time stamp. If they
differ by more than a small amount the request is rejected. This is
done for two reasons. First, it makes simple replay attacks on the
server, by someone who might be able to overhear traffic on your LAN,
much more difficult. Second, it makes it more difficult to request con-
figuration changes to your server from topologically remote hosts.
While the reconfiguration facility will work well with a server on the
local host, and may work adequately between time-synchronized hosts on
the same LAN, it will work very poorly for more distant hosts. As such,
if reasonable passwords are chosen, care is taken in the distribution
and protection of keys and appropriate source address restrictions are
applied, the run time reconfiguration facility should provide an ade-
quate level of security.
The following commands all make authenticated requests.
addpeer peer_address [ keyid ] [ version ] [ minpoll# | prefer | iburst
| burst | minpoll N | maxpoll N [...] ]
addpeer peer_address [ prefer | iburst | burst | minpoll N | maxpoll N
| keyidN | version N [...] ]
Add a configured peer association at the given address and
operating in symmetric active mode. Note that an existing asso-
ciation with the same peer may be deleted when this command is
executed, or may simply be converted to conform to the new con-
figuration, as appropriate. If the keyid is nonzero, all outgo-
ing packets to the remote server will have an authentication
field attached encrypted with this key. If the value is 0 (or
not given) no authentication will be done. If ntpdc's key num-
ber has not yet been set (e.g., by the keyid command), it will
be set to this value. The version# can be 1 through 4 and
defaults to 3. The remaining options are either a numeric value
for minpoll or literals prefer, iburst, burst, minpoll N, keyid
N, version N, or maxpoll N (where N is a numeric value), and
have the action as specified in the peer configuration file
command of ntpd. See the Server Options page for further infor-
mation. Each flag (or its absence) replaces the previous set-
ting. The prefer keyword indicates a preferred peer (and thus
will be used primarily for clock synchronisation if possible).
The preferred peer also determines the validity of the PPS sig-
nal - if the preferred peer is suitable for synchronisation so
is the PPS signal. The dynamic keyword allows association con-
figuration even when no suitable network interface is found at
configuration time. The dynamic interface update mechanism may
complete the configuration when new interfaces appear (e.g.
WLAN/PPP interfaces) at a later time and thus render the asso-
ciation operable.
addserver peer_address [ keyid ] [ version ] [ minpoll# | prefer |
iburst | burst | minpoll N | maxpoll N [...] ]
addserver peer_address [ prefer | iburst | burst | minpoll N | maxpoll
N | keyidN | version N [...] ]
Identical to the addpeer command, except that the operating
mode is client.
broadcast peer_address [ keyid ] [ version ] [ prefer ]
Identical to the addpeer command, except that the operating
mode is broadcast. In this case a valid non-zero key identifier
and key are required. The peer_address parameter can be the
broadcast address of the local network or a multicast group
address assigned to NTP. If a multicast address, a multicast-
capable kernel is required.
unconfig peer_address [...]
This command causes the configured bit to be removed from the
specified peer(s). In many cases this will cause the peer asso-
ciation to be deleted. When appropriate, however, the associa-
tion may persist in an unconfigured mode if the remote peer is
willing to continue on in this fashion.
fudge peer_address [ time1 ] [ time2 ] [ stratum ] [ refid ]
This command provides a way to set certain data for a reference
clock. See the source listing for further information.
enable [ auth | bclient | calibrate | kernel | monitor | ntp | pps |
stats]
disable [ auth | bclient | calibrate | kernel | monitor | ntp | pps |
stats]
These commands operate in the same way as the enable and dis-
able configuration file commands of ntpd. See the Miscellaneous
Options page for further information.
restrict address mask flag [ flag ]
This command operates in the same way as the restrict configu-
ration file commands of ntpd.
unrestrict address mask flag [ flag ]
Unrestrict the matching entry from the restrict list.
delrestrict address mask [ ntpport ]
Delete the matching entry from the restrict list.
readkeys
Causes the current set of authentication keys to be purged and
a new set to be obtained by rereading the keys file (which must
have been specified in the ntpd configuration file). This
allows encryption keys to be changed without restarting the
server.
trustedkey keyid [...]
untrustedkey keyid [...]
These commands operate in the same way as the trustedkey and
untrustedkey configuration file commands of ntpd.
authinfo
Returns information concerning the authentication module,
including known keys and counts of encryptions and decryptions
which have been done.
traps Display the traps set in the server. See the source listing for
further information.
addtrap [ address ] [ port ] [ interface ]
Set a trap for asynchronous messages. See the source listing
for further information.
clrtrap [ address ] [ port ] [ interface]
Clear a trap for asynchronous messages. See the source listing
for further information.
reset Clear the statistics counters in various modules of the server.
See the source listing for further information.
BUGS
ntpdc is a crude hack. Much of the information it shows is deadly bor-
ing and could only be loved by its implementer. The program was
designed so that new (and temporary) features were easy to hack in, at
great expense to the program's ease of use. Despite this, the program
is occasionally useful.
SEE ALSO
ntpd(8)
The official HTML documentation.
This file was automatically generated from HTML source.
ntpdc(8)